This invention relates generally to a power-supply circuit apparatus for high pressure gas discharge lamps for motor vehicles which is fed from a vehicle battery wherein the power-supply circuit apparatus has at least one voltage converter, connected with the vehicle battery and a vehicle ground connection, which produces a lamp supply voltage and/or an ignition auxiliary voltage and which is electrically-conductively coupled to an ignition device for igniting and operating high pressure gas discharge lamps.
A power-supply circuit apparatus is known from German patent document DE 34 45 817 C2 which has a circuit arrangement for operating a high pressure gas discharge lamp with low dc voltage. This power-supply circuit apparatus has at least one voltage converter connected to a vehicle battery and a vehicle ground connection. The at least one voltage converter produces a lamp supply voltage and/or an ignition auxiliary voltage, and is electrically-conductively coupled to an ignition device for igniting and operating a high pressure gas discharge lamp. In an embodiment shown in DE 34 45 817 C2, which is very complicated and cost-intensive, a supply-voltage pre-controller, which includes a dc/dc converter, is coupled to an ignition device of an ac-high pressure gas discharge lamp via a transistor invertor, a rectifier and a NF (low frequency) square-wave invertor. The circuit arrangement also includes supervising electronics which can detect deviations of supply voltage from a predetermined window range and turn off the power-supply circuit apparatus when such a deviation occurs. In addition, the supervising electronics offer polarity protection.
During operation of the power-supply circuit apparatus the cables, or connections, between individual components, and in particular connections to the ignition device, have voltages which can be dangerous for persons touching them. A person can come in contact with the cables when, for example, he attempts to do repair work, or when cables have become exposed in headlight areas or motor spaces of motor vehicles, for example due to an accident. It proves to be disadvantageous with circuit arrangements of the prior art that persons who touch live (having voltage applied thereto) parts of the power-supply circuit apparatus are not protected against electric shocks, thereby allowing for high potential danger for these persons.
It is an object of this invention to provide a power-supply circuit apparatus for high pressure gas discharge lamps in motor vehicles wherein persons, who touch live parts of the power-supply circuit apparatus, are protected as best possible, and wherein the power-supply circuit apparatus is dependably protected from malfunctions such as short circuits or excess currents.